Infuse a premium tequila like Patron Silver, which makes a difference to flavor and taste.
As always, make your own sweet & sour mix. I tend to like a more sour mixture than sweet, so I go with a 2:1 ratio. I strongly suggest you go with this ratio because if you are used to the sickening sweetness of store brands, you will be pleasantly surprised by how delicious homemade can be.
I chose not to salt the rim of the glass because I wanted my first jalapeño margarita to be a pure experience without salt changing the taste. That said, we all know tequila loves salt.
I always say to use the best liquor you can afford and Cointreau is delish, but if Cointreau is not in your budget, then triple sec will work fine.